Technical Field
The present disclosure relates to identifying areas of selection and non-selection on a multi-element capacitive device, and more particularly by using the capacitive values of the elements of the device to determine selection and shadow regions.
Description of the Related Art
Many consumer devices today such as iPhones™, iPad™, and smart phones, as well as other devices such as point of sale displays, use multi-element capacitive input devices to capture user input. These capacitive input devices usually include an insulator, for example glass, that is coated with a conductor and where touching the surface of the glass will distort the electrostatic field around the surface of the glass which is measurable as a change in capacitance. Many touch devices include a matrix of capacitive sensors or “cells.” In implementation, each individual cell, or cell-pair if the effective capacitance is measured between each pair, on the capacitive input device is able to provide a capacitive measure.
When an object, for example a portion of a finger, touches the surface of the capacitive input device, the capacitive measure of the multiple capacitive cells or cell-pairs near the surface of the touch shows a large value difference from the ordinary capacitance of the cells to indicate a touch. Taken together, these cells normally form a shape. Typically, when an application is using the capacitive device for input to determine where a user has made the selection through a touch, the application will look for the peak of the centroid of the shape or the one cell that shows the highest capacitive change. For example, when using a smart phone, most people when typing use the thumb tip which provides a smaller overall size and more compact shape of cells showing a large capacity value difference at a small area. Applications will then use the centroid of the shape to determine the location on the display that the user selecting.
Applications related to this functionality include: U.S. Pat. No. 6,483,931 to Kalnitsky et al., issued Nov. 19, 2002 directed to a planar fingerprint pattern detecting array; U.S. Pat. No. 6,512,381 to Kramer, issued Jan. 28, 2003, directed to an enhanced fingerprint sensing circuit; U.S. Pat. No. 6,496,021 to Tartagni et al., issued Dec. 17, 2002, directed to making a capacitive distance sensor including one or more sensor cells each with the 1st and 2nd capacitor plate; U.S. Pat. No. 7,239,227 to Gupta et al., issued Jul. 3, 2007, directed to a command interface using a fingerprint sensor input system.